Thermal and mechanical behaviour of refrigerated caverns in hard rock

摘要

One key issue in the design of unlined caverns for low temperature products is understanding the disturbance of the rock fracture network. Increasing aperture and extension of fractures inevitably affect the rock mass stability, the heat loss from stored products, and the risk of ice growth in cases when water invades the cavern. Consequently, it is essential that the designer of a refrigerated cavern has appropriate knowledge of the coupled thermal and mechanical behaviour of the fractured rock mass. Chalmers University of Technology in Gothenburg, Sweden has for several years, carried out research in the field of mechanical and physical phenomena of rock masses subjected to low temperatures. The main investigation was performed in a pilot scale cavern in hard rock, constructed as a vertical cylinder with a diameter of 7m and a height of 15m. The facility was equipped with comprehensive instrumentation, including approximately 200 temperature gauges and 140 deformation gauges. In the test, the temperature in the cavern was reduced in a stepwise manner to - 40℃, with comprehensive monitoring of relevant parameters such as relative humidity, air and rock temperature, rock strain, rock fracture aperture, cavern convergence and rock mass deformation. Prior to the field test, major efforts were made to predict the field results by analytical and numerical methods. The essential results of the theoretical analyses and the actual measurements of thermal and mechanical behaviour of the cavern are given in this paper.